#include <stdio.h>
#include <stdlib.h>

#include <math.h>

/*
 *
 */

int main(int argc, char** argv)
{
    /*dataseg*/
    int N;
    int R;
    int i;
    float *x;
    float *y;
    float length = 0;
    double PI = 2.0*acos(0.0);

    scanf("%d", &N);

    scanf("%d", &R);


    x = (float *) malloc(N * sizeof (float));
    y = (float *) malloc(N * sizeof (float));


    for (i = 0; i < N; i++)
    {
        scanf("%f", &x[i]);
        scanf("%f", &y[i]);
    }

    for (i = 0; i < N - 1; i++)
    {
        length += sqrt(pow(x[i + 1] - x[i], 2) + pow(y[i + 1] - y[i], 2));
    }
    length += sqrt(pow(x[N - 1] - x[0], 2) + pow(y[N - 1] - y[0], 2));
    length += 2 * PI * R;
    printf("%.2f", length);
    free(x);
    free(y);
    return (0);
}

Maybe because R must be real, not integer.